I. Field of the Invention
This invention relates generally to high-speed automated punch press for processing sheet metal and more particularly to the design of a punch assembly used in such machines.
II. Description of the Prior Art
In producing various products from sheet metal, it is often necessary to punch out predetermined hole patterns in the sheet metal workpiece. This is commonly done by a machine that positions a punch assembly and then employs a hydraulic ram to drive a sharpened punch point member of a predetermined shape through the workpiece and into a die underlaying the workpieces, thereby creating an aperture through the sheet metal of the predetermined shape.
After repeated strokes of the punch, the punch point can become dull and requires sharpening so that it is able to produce well-defined apertures. Repeated sharpening cycles remove metal from the punch point so that it can no longer punch through the workpiece and only serves to distort the workpiece, resulting in an undesired scrap rate. In most punch assemblies, when repeated sharpenings have been performed, it becomes necessary to replace the punch assembly's punch point with a new one, which is a relatively costly solution. Thus, a need exists for a way to increase the useful life of a punch assembly's punch point. The present invention satisfies this need.
Prior art metal punch assemblies have relied on the use of urethane strippers to allow punching close to non-flat workpiece surfaces. Such urethane strippers, however, suffer from the fact that they are incapable of accurately holding the workpiece during punching, resulting in misalignment of the punched hole. Also, urethane strippers are subject to rapid wear.